Removed duplicated code from bindings. Changed quote_xml() and quote_attrib() to use xml.sax.saxutils methods.
Added cdata() and strip_cdata() methods to stix.utils. EncodedCDATA class now always exports CDATA-wrapped values in to_obj()
Added missing import to bindings
Added some cdata unit tests
Remove unnecessary try/except
Cleanup
Merge pull request #217 from STIXProject/issue_10

Partial fix for issue 10: CDATA